black swan with red beak in koi fish pond, china

amur beak bills birds black blackswantheory blue both breeders carp china coloration colored colors cream cygnet decorative distinguished duties fish gardens group homosexual incubation informal japanese kept koi kois large males monogamous mostly orange outdoor pairings partners patterning plumage pond ponds purposes rearing red scalation share swan swans unusual variants varieties water waterbird white yellow